ORLANDO, Fla. - U.S. President Barack Obama was set to visit Orlando on Thursday to meet with survivors of the massacre at a gay nightclub and relatives of the 49 people killed, as a top intelligence official confirmed that no direct link had been found between the shooter and foreign terror groups.

Omar Mateen, 29, a U.S. citizen born in New York to Afghan immigrants, also wounded 53 people in a three-hour rampage inspired by Islamic State militants that stands as the deadliest mass shooting in modern U.S. history.

CIA Director John Brennan told a Senate Intelligence Committee hearing that the agency "not been able to uncover any direct link" between Mateen, who was shot dead by police, and foreign terror groups.

Mateen claimed allegiance to a variety of militant Islamist groups, including some at odds with each another, in a series of phone calls to 911 emergency services and a local cable television news channel during his rampage.

The Federal Bureau of Investigation has interviewed Mateen's second wife, Noor Salman, who knew of his plans, according to a law enforcement source, and prosecutors were preparing to present evidence against her to a federal grand jury.

Salman has not commented publicly since the attack, which began around 2 a.m. Sunday.

"We're working with our law enforcement partners to find out everything that we can about what happened at the Pulse nightclub," Lee Bentley, the U.S. Attorney for Florida's middle district said on Wednesday. "We are using all law enforcement and legal tools to reconstruct not only the events of that night but the events of the past several months."

Obama, accompanied by Vice President Joe Biden, was to travel to Orlando in the latest in a long list of trips he has taken to console victims of mass shootings during his 7-1/2 years in office. In December 2015, a married couple inspired by Islamic State shot dead 14 people in San Bernardino, California.

"This will be, I think, an emotional trip," White House spokesman Josh Earnest told reporters. "The president recognizes that he is a symbol for the rest of the country. But it would be impossible for him not to be personally affected by these kinds of conversations."

Some 23 of the wounded remain hospitalized, with six in critical condition, according to Orlando Regional Medical Center.

During his attack, Mateen also posted messages on Facebook. One of them said, "You kill innocent women and children by doing us air strikes ... now taste the Islamic State vengeance," according to a letter to Facebook from the chairman of the U.S. Senate Committee on Homeland Security seeking more information on Mateen's history on the social media network.

Mateen carried out the slaughter with a legally purchased assault weapon and handgun despite twice being investigated by the FBI for alleged connections with terrorist groups.

RENEWED DEBATE ON GUN CONTROL

The mass shooting renewed debate in Washington about gun control. Some Republicans including presumptive presidential nominee Donald Trump and U.S. Senator Pat Toomey, a Republican from Pennsylvania, suggested that people on federal watch lists who are banned from flying on commercial jets should not be allowed to purchase firearms.

U.S. Senator Chris Murphy, a Democrat from Connecticut, ended a filibuster after nearly 15 hours early Thursday morning, saying Republicans agreed to hold votes on measures to expand background checks and prevent people on U.S. terrorism watch lists from buying guns.

Democrats have been unsuccessful in trying to pass national-level gun control measures after past mass shootings, including the 2012 attack on a Connecticut elementary school that left 26 people dead, including 20 young children.

The Second Amendment of the U.S. Constitution protects the right to own firearms, which has been passionately defended by the powerful National Rifle Association as well as many Americans.

The NRA said on Wednesday it agreed that "terrorists" should not be allowed to own firearms but made clear it believed people on watch lists should have an official right to appeal their status.

The first memorial for a victim of the massacre, a wake for Javier Jorge Reyes, was held on Wednesday evening at a funeral home near a four-lane highway just south of Orlando.

Motorists honked their support for those attending, including many who held signs or wore T-shirts reading: "Orlando Strong," an echo of the "Boston Strong" slogan after that city was hit by a deadly bombing attack in 2013.